A ban ends the banned person's turn at once and takes them out of the queue #195

Part of #13 (owner: "Banned users are dropped from the queue and their turn ends").

Done:

• [ ] When a ban lands, the banned person's turn ends (the arm holds, as when the owner ends a turn), they are removed from the queue, and everyone's queue view updates.
• [ ] They can still watch, and a rejoin is refused while banned.
• [ ] Test in src/lobby.test.ts: alice drives and bob queues; ban alice; bob is next, alice is not in the queue, and alice's join is refused.
• [ ] forge.json untouched; bun --cwd Software/so101 test passes.

Unstuck: this no longer waits on #227. The owner can already ban over /live on main, so a ban ending the turn can be built and tested with the owner's ban. When #227 lands, a moderator's ban reaches the same code.